An investigation will be carried out on the failed New Lynn culvert and the Ardmore Treatment plant that is struggling to filter dirty flood waters.
Auckland mayor Phil Goff met with affected families and business owners in New Lynn last night.
An automatic investigation would be carried out, he said.
"You've got to find out what's happened. What's caused it. Could it have been prevented? Could it have been mitigated against?
"We'll be looking at the challenges of the dams in the Hunuas and the inability of the water filter station at Ardmore to be able to cope with that.
"Our city deserves a water supply that can be relied on 100 per cent of the time."
Goff cited Auckland's population growth of 45,000 a year, less ability to move from one source of unfiltered water to another, and more extreme weather events due to climate change as adding strain to current infrastructure.
Around $100 million has already been spent on stormwater infrastructure renewals over the last five years.
A weather bomb had never overwhelmed the current infrastructure before, Goff said, "but because it's happened now we have to think about ways we can improve the resilience of the system to cope".
This week 27 people have been put up in emergency accommodation by Auckland Council due to the flood waters. Replacement clothes and furniture are being found for those who need it and loaded HOP cards were distributed to help people get to work.
"It'll make a world of difference if we can give them a helping hand," Goff said.
"We're not going to leave anyone in the lurch."
Goff admitted the New Lynn culvert on Gardner Ave had failed. The grill that covers it had collected debris which made it overflow.
Council officials assured Goff that immediately before the deluge they had inspected the culvert and it was clear. Goff was waiting for an engineering report to see if the culvert needs to be replaced.
"Those sorts of things are never cheap. You've got to dig up the whole road way."
Whau councillor Ross Clow said there had been an underinvestment in all of Auckland's stormwater infrastructure. The damage means another culvert is likely needed to increase capacity, he said.
"The bottom line is we've got an infrastructure gap and we've just got to prioritise things... We don't have the capacity."
Residents in the New Lynn, Titirangi, Glen Eden and neighbouring areas were busy cleaning out garages and their homes yesterday following devastating floods over the weekend.
Among them Abdullah Mehri, his brother and his parents. They had already escaped fighting in Afghanistan and the Christchurch earthquake.
On Sunday, torrents of water poured towards their home, which is in a dip, from the culvert at the back, from the street and from their neighbours property.
They thought they were trapped as they watched the chaos from upstairs. If they had left the house the water would have been up to their chest.
"It was a shock to be honest. I never thought this flood would happen," Mehri said.
A young Tongan family who live on the bottom floor of the same property were not so lucky. The floods swept through their home and ruined everything.
The couple were at church with their children, aged 2 and 3.
"When they came back home everything was just devastated," Goff said.
The council has put the family in accommodation for a week and the Salvation Army are finding replacement clothing and furniture.
The family are just one of the many "human tragedies" that have been borne out of the catastrophic weather event, Goff said.
MetService meteorologist Philippa Murdoch said that the rain will have mostly eased off on Tuesday. A ridge of high pressure is then expected to descend over the country later in the week bringing settled, sunny weather.